Objective. To assess cognitive and behavioral outcome in treated maternal phenylketonuria (PKU) offspring.
Methods. In this prospective, longitudinal study, 228 children who were born to mothers with treated PKU or untreated mild hyperphenylalaninemia were compared with 70 control subjects at 7 years of age.
Results. Offspring cognitive outcome negatively correlated with the number of gestational weeks that elapsed until maternal metabolic control was achieved (r = −0.61). Behavioral outcome was similarly affected. Postnatal measurement of stimulation in the home was also related to offspring IQ.
Conclusions. Children who are born to mothers who have PKU and attain metabolic control before or very early in pregnancy seem to begin life with undiminished potential. Delay in attainment of maternal metabolic control is associated with declines in offspring developmental outcome. The postnatal environment also significantly affects outcome. Interventions to improve dietary compliance before and throughout pregnancy as well as interventions to improve the postnatal home environment may reduce the risks associated with maternal PKU.